Isolation and antibiogram of pathogenic bacteria (Escherichia coli, Salmonella sp.& Staphylococcus sp.) from different kinds of cheese available in market of Chattogram in Bangladesh.

Abstract

Cheese is a solid, fresh or ripened product obtained by adding the enzyme rennet in the presence of lactic acid produced by the adventitious microorganisms that causes coagulation and whey separation of milk, cream or partly skimmed milk, buttermilk. Cheeses of different types especially soft and semi-soft are suspected to the presence of pathogenic E. coli, Staphylococcus sp., Salmonella sp. etc which are harmful for public health. The purpose of the current research was to investigate the qualities of cheese collected from super-shops of Chattogram. A total of 15 cheese samples were collected from three super-shops of Chattogram named as shop-A, shop-B and shop-C. Among 15 cheese samples, the S3 sample collected from shop-B had the highest bacterial load (1.80×107 cfu/ml) than those in shop-A and shop-C. Isolation of pathogenic E. coli, Staphylococcus sp., Salmonella sp. was done by using selective media such as EMB agar, MSA, XLD agar respectively. Four out of the total 15 cheese samples were found to be contaminated with E. coli (26.67%) while 1 sample was contaminated with Salmonella sp. (6.67%) & ten were detected as contaminated with Staphylococcus sp. (67%). The antibiotic susceptibility test was done by Kirby-Bauer method to detect susceptibility to ampicillin, amoxycilin, gentamicin, ceftriaxone, ciprofloxacin and tetracycline. E. coli, Staphylococcus sp., & Salmonella sp. showed almost 100% resistant behavior to ampicillin, amoxycilin, tetracycline & 50% sensitivity of E. coli to gentamicin and ciprofloxacin while for Staphylococcus sp. sensitivity to gentamicin, ceftriaxone, ciprofloxacin was 27.27%, 90.91%, 18.18% respectively. The CS test results were highly significant for ceftriaxone (p=0.003; i.e. p<0.05). The screening for shiga-toxin strains in E. coli isolates was based on the detection of the two genes stx1 & stx2 and tetracycline resistant strains of E. coli were detected for Tet A, Tet B & Tet C genes by polymerase chain reaction (PCR). The prevalence of stx1 was found 25% while for stx2 50%. The prevalence of resistant genes specific to Tet A, Tet B of E. coli for cheese samples was 100% (0.40-1.00 % CI) in 95% CI whereas for Tet C, prevalence was 50% (0.07-0.93 % CI) in 95% CI. In conclusion, the risk of pathogenic bacteria is higher in cheese if safety measures not maintained & could pose a massive health risk.